1. Field of the Invention
The present invention relates generally to framing systems used in the construction of buildings, and more particularly to a metal framing system which incorporates hollow metal tubing.
2. Related Art
Known framing systems used in the construction industry are typically made of either wood or metal, with wood framing systems being the most common. As is well known, wood framing systems have enjoyed widespread use, for instance in the construction of residential homes. Wood frames are typically constructed by connecting pieces of wood, such as 2.times.4's or 2.times.6's, with nails in a form that creates either the interior or exterior outline of a structure, or both. In known wood framing systems, all major components are typically made of wood, including components which may be referred to in the art as the bottom plate, studs, top plate and roof trusses. With the exception of roof trusses, which utilize miter cuts on the ends of adjacent pieces of wood to accomplish the desired angular relationship between adjacent members, most wood framing systems consist primarily of straight 2.times.4's nailed together to define the outside and inside areas of the structure and to provide the load bearing support.
Although wood framing systems have enjoyed widespread use, they are subject to several disadvantages. For instance, the process of constructing a wood framing system is relatively slow since all joints within the system are typically connected with several nails. For example, even if the included roof trusses are pre-assembled, it typically takes a framing crew of four people between five and seven working days to frame a 1,500 square foot house.
Furthermore, the quality of the workmanship associated with the construction of wood framing is often poor, especially in conjunction with low and moderate priced housing where builder's profit margins are relatively low and building costs are suppressed as much as possible. The primary result of this poor workmanship is typically the lack of squareness in the structure frame which adversely affects the installation of other components in the structure.
Other disadvantages associated with wood framing is the flammability of wood, and the potential for deterioration due to exposure to weather or insects such as termites or carpenter ants. Another disadvantage is that the system strength may be reduced at angled connections which require a miter cut and attachment with either nails or screws. Yet another disadvantage associated with use of wood framing systems is the depletion of wood as a natural resource.
Although metal framing systems may represent an improvement relative to wood framing systems with regard to improved strength and reduced deterioration, known metal framing systems are also typically subject to one or more disadvantages. For instance, like a wood framing system, the assembly of a metal framing system may be very time consuming since the metal framing system may require nearly as many metal screws as the nails used in a comparable wood framing system to connect adjacent metal components. Moreover, the screws are generally not as quickly inserted as nails, and therefore the metal framed structure may actually require more time to assemble than a comparable wood framed structure. These and other disadvantages associated with metal framing systems may be further illustrated by the following discussion of known metal framing systems.
Metal framing systems have been used for some time in commercial construction and have recently become more popular in residential construction. Known metal framing systems used in these applications commonly include metal components which are formed as three-sided channels, such as U-channels. For instance, these systems may include vertically extending metal channels, which are inserted into the open side of horizontally extending metal channels used for the bottom and top members of the metal framing system. The joints between the vertically and horizontally extending members are typically secured with numerous fasteners such as screws. Additionally, metal straps are often utilized to secure the vertically extending channel members to one another. Accordingly, the assembly of a metal framing system of this type may be very time consuming due to the requirement to secure the numerous fasteners and metal straps.
Another known metal framing system, which is used to frame a carport, utilizes round hollow tubing with one end of each of the round tubing members being inserted into the hollow end of an adjacent round tubing member. The joint between the two round tubing members may then be stabilized with conventional fasteners. The male portion of each joint may be accomplished by a swaging process to reduce an end portion of the corresponding round tubing member. Although the foregoing carport framing system has been advantageously utilized, use of round metal tubing makes it difficult to insert fasteners into the tubing joints which complicates the assembly of the framing system. Furthermore, in some applications, such as when the carport is placed adjacent to a residential structure, the carport frame may not be viewed as aesthetically appealing.
It is often more advantageous to use either square or rectangular metal tubing in certain applications. However, the connection of adjacent components of square or rectangular metal tubing has been subject to the following problems. Known methods of reducing square and rectangular metal tubing include those which utilize one or more dies. With this form of reduction, one end of the square or rectangular tube is crushed by the force created by various configurations of press equipment, with the size of the reduction being determined by the die design. This method of end reduction of square and rectangular metal tubing is subject to the following disadvantages. In the first instance, the end reduction of the tubing may require several "hits" or applications of the press equipment to achieve the desired reduction, with each application adding to the manufacturing cost. Furthermore, the crushing force of the press equipment may cause excessive and/or non-uniform deformation of the tube end. More specifically, one or more sides of the tubing may become concave, thereby reducing the overall strength of the tube and detracting from the smoothness of the transition between the original shape and the reduced end. In certain instances, the excessive and/or non-uniform deformation may be so severe that the reduced end of the tube is not capable of insertion into a tube of the same size prior to reduction, as intended.
Due to the foregoing problems associated with the use of dies to end reduce square and rectangular tubing, connections of adjacent lengths of like-sized square and rectangular metal tubing has generally been accomplished by inserting a smaller tube, of the same shape, inside two adjacent like-sized pieces of rectangular or square metal tubing, and then securing the joint by fastening each section of the outer tubes to the inner tube. Framing systems of this type have been used to frame carports. The inner tube, as well as the required fasteners, add to the cost of this method of joining adjacent sections of square or rectangular metal tubing. Another disadvantage associated with this type of metal framing system is that the strength of the included joints may be be limited to the strength of the required fasteners at each joint.
In view of the foregoing disadvantages associated with known wood and metal framing systems, there is a continuing need for improved framing systems for use in the construction of a wide variety of buildings including residential and commercial structures.